nitrite and nitrate levels

[jillswindoll]

My system is finally completely up and running! I had about 60 koi in a 1000-gallon tank for several months and for the majority of that time I did not have a pump running. The water was green (no surprise there!) but about half of the surface was covered with water hyacinth and the fish seemed very happy. My ammonia, nitrite, and nitrate levels have always been zero. Then I added some bacteria that I got from Paula Speraneo of S&S Aquafarm.

I finally got a timer and I ran the system through a 8'x4'x1' bed with no plants in it. The algae started to bum me out so I decided to tackle that problem before I added plants. I removed all of the water hyacinth, covered the pond with black landscape fabric and stopped feeding the fish for four days. I added a small additional filter to add a bit more air and hopefully get rid of some of the green crud. Water chemistry looked good, too.

It worked! I had such crystal clear water that all I wanted to do was sit and look at it all day!! I was so proud!

I added about fifty lettuce plants last week and they seem happy. The problem now is that now, for the first time ever, I have nitrite readings of 0.25ppm and nitrate levels of 5.0ppm. I lost two fish this weekend!

Before I discovered this problem I was actually worried about not having enough fish since my experience with these fish has always been zero readings of ammonia, nitrite, and nitrate. What gives??? My first thought was that now that the algae and water hyacinth are gone there isn't enough plant life to take up the waste products. But if that was the case don't you think my lettuce would be growing like crazy instead of just seeming happy?

Thanks!







It worked

[Ravnis]

Sorry about your fish!

The water hyacinth and possible the algae were "eating the ammonia". Nitrates of 5 is ok and the nitrite of 0.25 should not be that much of a problem.

This ia a guess...with the ammonia going straight to the plants you may not have set up the general conversions of ammonia to nitrite , nitrite to nitrate. Water plants can use the ammonia directly and literally starve the nitrifying bacteria. The fact that you did not have nitrate levels before and now are seeing some is more evidence that the cycle is establishing and fast. I am running minnows with nitrates in the 30 -40 range and they are currently doing fine after the stress of coming from the bait shop to there new home.

A wise man on this board said something to the effect of... do changes in small steps and slowly. The sudden lack of filtering, shade, loss of algae(they shade the beneficial bacteria from the sun) might have caused a temporary imbalance that led to the deaths. Again this is still a guess.

[Outbackozzie]

+1 for above, and was there aeration to the pond while the cover was on? If not I would blame lack of oxygen for the deaths.

[Jonathan Dyer]

pH Guys pH what is your pH readings? If the fabric was on the water stopping the fish from getting air from the surface I would agree with Ozzie. 60 Koi in 4500L of water there should never be a problem with o2 levels even without a pump unless they couldnt gasp for air at the surface. Test your pH, much more important than your low readings of nitrogen. Your system would have cycled without a dout the bacteria would be growing on the plant roots, walls of the tank, and any other place suitable. I do recomend adding Salt to your system say 9lb, but that is English pounds is there a difference between US and England weights.

[GaryD]

Hi,

....I would blame lack of oxygen for the deaths

Me too!

Gary

[jillswindoll]

Thanks for your replies! I had no idea that the water plants could use the ammonia directly!

pH is fine, it has ranged between 7.2 and 7.6 over the past six months.

As for oxygen, the water level is about six inches below the landscape fabric and it rests on a web of fishing line I made to keep the fabric off the surface of the water. There is a place where there is no cover, where the water returns to the tank, that is about 2ft^2 (about .2 square meters). I don't know if this is sufficient. Let me know what you think...I would rather have pea soup for water than dead fish!!

If the bacteria were growing all over the plant roots and I removed them all at once then I might have really put a dent in the bacteria population. I have a LITTLE more of that culture left that I can add in there this morning.

You know, I was thinking of taking the remaining culture (enough for ~1/4 of the volume in my tank) and putting it in a larger container with some pond water and leaving it on the shelf to multiply...that should work, right??

I will add salt as well. I have read that it is very good for the koi to add salt to the water but I always wondered about adding salt to an aquaponics system. What effect will it have on the plants/roots in the growbed?

You guys rock! Thanks for all of the great advice!

[Outbackozzie]

up to 3kg of salt per 1000 litres is fine. All plants except for strawberries seem to do ok.

[Jonathan Dyer]

As for oxygen, the water level is about six inches below the landscape fabric and it rests on a web of fishing line I made to keep the fabric off the surface of the water. There is a place where there is no cover, where the water returns to the tank, that is about 2ft^2 (about .2 square meters). I don't know if this is sufficient. Let me know what you think...I would rather have pea soup for water than dead fish!!

I don’t see an issue whatsoever. Your fish had ample access to air, remember Koi and Goldfish are able to breathe large amounts of air from the atmosphere I would find it hard to believe that they died due to lack of oxygen as your return line is also adding additional oxygen as well.

If the bacteria were growing all over the plant roots and I removed them all at once then I might have really put a dent in the bacteria population. I have a LITTLE more of that culture left that I can add in there this morning.

I wouldn’t be to concerned about this as there will be enough bacteria elsewhere on the walls, bottom gravel if you have any, rotting debris on the bottom but, 60 fish in 1000 gallons really isn’t enough to have high readings of nitrogen anyway I have over 100 Koi in 500 gallons with ammonia/nitrite readings Zero and nitrate around 40ppm (I still have to add more fertiliser to get good plant growth). You experienced the same sort of thing 60 fish even at 12” long per 1000 gallons is nothing (how large are your fish anyway?) the dilution rate and waste they produce is not much at all, you will have an active bacteria population that converts waste very quickly you just don’t have enough waste to get much of a reading, although your water Hyacinth would have been supporting a large percentage of the bacteria so there could have been an issue. As for your recent readings of nitrite 0.25ppm and nitrate levels of 5.0ppm the algae and hyacinth is able to uptake ammonia directly from the water as discussed, as do most other water plants (duckweed, azolla) they would have had a large effect on the uptake of nutrients but, you have done some major changes to your system in a short time this alone will have put things out of balance and needs time to recover causing excessive stress on your fish. During these times of stress contrary to what people say or recommend, feed is very important sometimes during periods of stress fish go off there food and adding more food can cause poorer water quality = more stress but is a very poorly managed fish tank if this be the case; but if one sees that the fish does not go off there food I would never stop feeding especially for a Koi it can be detrimental, I would even give a sick fish just a bit of food even if they wouldn’t eat it, fish husbandry is about 90% observation. Perhaps you lost those fish due to excessive stress and lack of food; remember Koi don’t have a stomach as such so they need little bits of food often; I feed my Koi around 5 times a day.

You know, I was thinking of taking the remaining culture (enough for ~1/4 of the volume in my tank) and putting it in a larger container with some pond water and leaving it on the shelf to multiply...that should work, right??

Generally no and not necessary. Doing this will not achieve anything, for one the bacteria need lots of oxygen so continuous aeration would be needed secondly the bacteria needs something to adhere in order to colonise gravel, sand, plant roots are classic examples and the more surface area the larger the colony of bacteria will be, thirdly the bacteria needs a source of ammonium to start the cycling process adding a small amount of urea 1teaspoon per week would be needed. So therefore, doing this would not achieve much I would even say that most of the bacteria would die anyway unless of course you added air, bio-filter and urea, just add the water to your tank it wont hurt much.

I will add salt as well. I have read that it is very good for the koi to add salt to the water but I always wondered about adding salt to an aquaponics system. What effect will it have on the plants/roots in the growbed?

9 pounds of Salt in 1000gallons should not affect your plants at all, 9 pounds would be perfect for Koi but I would never go much over 18 pounds at this rate plants like strawberries and beans may have adverse affects as well as causing a bit more osmotic imbalance to your Koi.

[jillswindoll]

Can I use Kosher salt or should I use special aquarium salt?

I guess I did make a lot of big changes in a short period of time...

[Jonathan Dyer]

Honestly it doesn’t really matter too much what type of salt you do use. But I have used specially designed ‘Aquarium Salts’ for Goldfish and Koi in the past, how much better it is than common table salt I don’t know but according to the labeling it should have an edge. Kosher salt is and will work just as good, I don’t mind sea salt as it has other minerals and trace elements as well as increasing hardness levels of the water, I have used iodised salt with no ill effects many times. At the end of the day I think any type of salt is better than no salt in a system the health benefits to your fish is tremendous, I have never lost a fist to date and the salt I run (1000ppm maintenance level) in my system is I think the reason why.